A major challenge in today's information technology (IT) environments is energy efficiency. This is reflected in the fact that most of today's Green IT Projects aim to increase the efficiency of IT environments such as datacenters and data communications networks in general. There are various ways to increase efficiency, for example using advanced cooling systems in datacenters, or by virtualization of network devices whereby a single physical machine is logically partitioned into plural virtual machines. An apparently simple idea for improving efficiency is the decommissioning of unused hardware. The practical implementation of this idea, however, is by no means trivial. A key question is how to identify underutilized devices, i.e. those which are unused or not being used to a desired level, bearing in mind the number of devices, services, and overall operational complexity of a typical networked system. A datacenter, for example, may contain thousands of computer systems hosting many thousands of services. One known technique is to perform monitoring on each individual device to track utilization, normally by monitoring the state of the main processor, network interface, disk drive or any other component with a variable usage pattern. The monitoring process is complex, however, and the technique is difficult and time-consuming to set up if not already installed in the required systems in a given network. A network administrator might also assess device utilization by detailed analysis of an IT inventory. However, a sufficiently accurately maintained inventory, or indeed any inventory at all, may not be available. As with post-installation of individual device monitoring systems, producing an appropriate inventory specifically for purpose would likely be too much effort or prohibitively expensive.